In recent years, use of automatic manufacturing processes has become increasingly prominent in industry. The need for robots to perform an ever-widening variety of tasks has created a demand for more sophisticated robotic equipment. For example, one desired feature for certain robotic applications is that the robot have tactile sensing capabilities. With such capabilities, a robot can hold an object under a controlled gripping pressure, and in some cases identify the object being held.
One example of tactile sensing is shown in U.S. Pat. No. 4,555,954 to Kim granted Dec. 3, 1985. Kim teaches a circuit board 102 with a plurality of spaced apart conductive foils 104, each of which is connected to a decoder 106 for selectively applying voltages through individual foils. An anisotropically conductive pad 107 has electrically conductive strips 108 overlying foils 104, but separated from the foils by up-raised insulative portions 116. Each of strips 108 is connected to a multiplexer 115. Conductive strips 108 are deformed responsive to application of force, so that the location and magnitude of the applied force can be determined from the voltage at the multiplexer output.
U.S. Pat. No. 4,555,953 to Dario et al granted Dec. 3, 1985 shows a sensor having a superficial layer 1, a deep sensing layer 2 and an intermediate layer 3 between layers 1 and 2. The deep sensing layer includes an upper layer of a ferroelectric polymer, and a series of metal electrodes 6 beneath film 4. The superficial layer includes a plurality of metal electrodes 20 sandwiched between two layers of a ferroelectric polymer.
These tactile sensors are satisfactory for certain objectives, for example qualitatively sensing material hardness, surface texture or slippage. However, their high cost tends to discourage their use in all but a few specialized cases. Consequently, they are unable, in practical terms, to enhance the safety in general automatic manufacturing processes through widespread use.
Therefore, it is an object of the present invention to provide a tactile sensor for robotic equipment that enhances safety for robotic equipment, workpieces, and especially for operators working near the equipment.
Another object of the present invention is to provide a tactile sensing structure sufficiently low in cost for application to a robotic arm or other movable member as a "skin" covering substantially the entire surface area of the arm or member.